The field of the invention pertains to bubble levels used by stone masons, bricklayers, carpenters and other tradesmen in the construction trades. In particular, the invention pertains to solidly constructed levels that will retain their accuracy under constant use in wet, dusty and dirty environments and where the level may also be accidentally dropped.
Tradesmen typically have several levels of various lengths. To lessen the need for several separate levels, extendable or telescopeable levels have been developed. U.S. Pat. No. 4,130,945 discloses an extension level wherein extension members carrying spirit level vials overlap on a central base member having a leveling vial therein.
U.S. Pat. No. 4,894,925 discloses an extendable level of generally open web construction and stops to prevent over-extension. The level provides for a planar relationship between the level edges.
U.S. Pat. No. 5,577,327 discloses a central portion having a horizontal spirit vial and end portions with vertical spirit vials. The end portions telescope on rods extending from the central portion.
U.S. Pat. No. 6,041,510 discloses a three-piece level wherein two side pieces slide on a central body to provide more than doubling of the fully collapsed length.
The new level provides for a very rigid and rugged construction in the form of solid blocks between four track members that guide the relative movement of the level frame and level extension. The track members and extension provide planar surfaces the length of the extended level on the top and bottom. The major parts of the level are exceptionally simple in configuration and in ease of assembly, thus providing for very inexpensive manufacture.
The extension includes handgrips to assist in both extending and using the level. As an option, a rotatable spirit vial is located in the extension. The rotatable spirit vial may be set for any angular degree between the horizontal and the vertical. Thus, angular pitches may be accurately determined with as much ease as the horizontal or vertical.